1. Field of the Invention
The present invention relates to an information processing apparatus, and more particularly to an image processing apparatus, which has an energy saving mode function and is connected with an external device through a network. In addition, the present invention relates to a method for controlling an information processing apparatus, and a computer readable medium storing instructions for performing the method.
2. Discussion of the Background
Recently, network systems are popularized, in which plural information processing apparatus such as computer and printers are connected with a network such as Ethernet™ and LANs to perform data communication therebetween. As one of such information processing apparatus, published unexamined Japanese patent application No. 2005-267100 discloses an image forming apparatus which includes a main CPU (central processing unit) and a sub CPU to process data received from external devices, wherein the powers to one of the main CPU and sub CPU, and part of the apparatus temporarily turn off to reduce the power consumption thereof.
In this background image forming apparatus, when a power saving mode is adopted, the main CPU turns off while the sub CPU, which has a relatively low power consumption, performs predetermined controlling processing and data processing (such as processing of packets received from external devices) to reduce the power consumption. However, when the received data cannot be processed by the sub CPU or when it is necessary to establish connection with the sender upon receipt of a packet such as TCP (Transmission Control Protocol), the main CPU has to be returned to the standard power mode to process the received data. Therefore, every time similar data are received, the main CPU has to be returned to the standard power mode to process the data independently of the contents of the data. Accordingly, the image forming apparatus cannot maintain the power saving mode for a long time, thereby lessening the power saving effect of the apparatus.
In addition, periodical query protocols using TCP such as WSD (Web Service on Devices), which have been seldom used, are broadly used recently. Therefore, it is necessary for such an image forming apparatus to frequently return the main CPU to the standard power mode, resulting in shortening of the period during which the main CPU is in a power saving mode (i.e., the period during which the main CPU is in the standard power mode increases). Thus, in such conventional information processing apparatus having a power saving mode function, the power saving mode cannot be maintained for a long period of time and therefore the apparatus produce a little power consumption reduction effect.
Because of these reasons, a need exists for an information processing apparatus, which can change the power consumption mode from a standard power mode to a power saving mode or vice versa, wherein the frequency of changing the mode from the power saving mode to the standard power mode is decreased (i.e., the power saving mode can be maintained for a relatively long time) to enhance the power saving effect thereof.